Abstract
Simple SummaryThe present study, in view of the importance of finding an alternative hormone to eCG, aims to determine the response of sheep to hCG-based treatments. The findings indicate that the low fertility rates reported for protocols based on the administration of hCG for inducing ovulation during estrus synchronization in sheep may be related to a high occurrence of abnormal follicular growth patterns, disturbances, and retardments of ovulation and concomitant formation of follicular cysts in the treated females. These results preclude their practical application to induce ovulation concomitantly to estrous synchronization treatments.Currently, there is an intense effort to find an alternative hormone to eCG to induce ovulation after estrus synchronization treatments in sheep. One of the proposed alternatives is based on the use of hCG, but the results are controversial since fertility rates are commonly affected. The present study aims to evaluate, therefore, the adequacy of hCG in protocols for the synchronization of estrus and ovulation. Ovarian follicle dynamics, occurrence of estrus behavior and subsequent ovulation, quality of corpora lutea, and pregnancy rate after controlled natural mating were assessed in two consecutive trials. The findings indicate that the low fertility rates reported for the protocols based on the administration of hCG for inducing ovulation during estrus synchronization in sheep may be related to a high occurrence of abnormal follicular growth patterns, disturbances, and retardments of ovulation and concomitant formation of follicular cysts in the treated females. These results preclude their practical application to induce ovulation concomitantly to estrous synchronization treatments.
Highlights
Only 8 of ewes (61.5%) showed estrus signs in the group treated with human chorionic gonadotrophin (hCG), but ovulation and subsequent presence of corpora lutea (CL) at Day were observed in 11 of the 13 sheep (84.6%)
Similar results were found in the second trial, in which all the sheep in Group equine chorionic gonadotrophin (eCG) but only 7 of 16 ewes in Group hCG
The ovarian scanning performed of the subsequent estrous cycle showed that all the ewes in Group eCG and 15 of 16 (93.7%) in Group hCG showed the presence of CL at Day 14 after CIDR removal
Summary
HCG was earlier used for inducing ovulation during the anoestrus season in sheep [7] and tested afterward for its incorporation to protocols for estrus synchronization in heifers [8] and ewes [9]. These first data in sheep supported that hCG administration increased prolificacy but decreased fertility. More recent data support that sheep treated with hCG, in spite of inducing more synchronized ovulation than controls without gonadotrophin treatment, had a reduced pregnancy rate after TAI [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
